18-03-2011, 06:41 PM
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| M.Arsalan Qureshi | | Join Date: Oct 2008 Location: Garden Town, Multan Cantt
Posts: 616
Program / Discipline: BSTS Class Roll Number: 09-31 | |
Multimedia Multimedia * Cryptography is the science and art of transforming messages to make them secure and immune to attack. * Encryption renders a message (plaintext) unintelligible to unauthorized personnel. * Decryption transforms an intentionally unintelligible message (ciphertext) into meaningful information. * Cryptography algorithms are classified as either symmetric-key methods or public-key methods. * In symmetric-key cryptography the same secret key is used by the sender and the receiver. * Substitution ciphers are either monoalphabetic or polyalphabetic. * The P-box, S-box, and product block are methods used by block ciphers. * DES is a symmetric-key method adopted by the U.S. government, but it has been replaced by Triple DES or other methods. * Operation modes to handle long messages include ECB mode, CBC mode, CFM, and CSM. * In public-key cryptography, the public key is used by the sender to encrypt the message; the private key is used by the receiver to decrypt the message. * One of the commonly used public-key cryptography methods is the RSA algorith.
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